Slowly rotating polyphase synchronous generators for service in wind power plants are known. Direct driven generators of the above type for wind power plants generally rotate at relatively slow rotational speeds in the range between 20 rpm and 40 rpm. At an output power of approximately 1 to 2 MW, the rotational speed is even lower, in the range of approximately 10 to 25 rpm. Known polyphase synchronous generators of the above mentioned type are used in the wind power plant models E-40 or E-66 of the Enercon Energieanlagen GmbH.
In these wind power plants the polyphase synchronous generator possesses a ring-shaped stator, inside of which a rotor is free to move. This rotor is connected directly, without the interposition of gears, to the rotor of the wind power plant. The rotor is executed as a salient-pole machine and comprises a multitude of poles with pole shoes, also known as pole pieces.
The objective in the construction and design of the generator is to, as much as possible, reduce noise generated during the operation of the wind power plant, so that the impact on the environment may be reduced, and the general acceptance of wind power plants may be improved.
Conventional generators can not always achieve the required low noise emissions since they are subject to strong mechanical vibrations during operation, which can be transferred to other components of the wind power plant, such as the rotor, the nacelle, and the tower, and there can lead to unwanted noise emission. Noise emission is especially high when the stator of the generator or other components are stimulated to vibrate at their so-called natural frequency.
The objective of the present invention is to specify a method, a generator, and a wind power plant, that eliminate the above mentioned problems.
This objective is met by a method and a synchronous generator having the features as defined in claims 1 and 4. The secondary claims describe preferred further developments.